The title suggests the unthinkable: superindulgence in fare that has often been considered a frippery. Waffles can seem, quite appealingly, the stuff of childhood kitchens and adult narcoleptic Sundays. But Greenspan, a food journalist, tries to move waffles into the culinary mainstream, where they can serve a purpose at almost any meal, and in between. She discusses proper equipment, appropriate pantry purchases, unusual dietary considerations and how waffles can accommodate them, and what to do with waffles made ahead of time--freeze and microwave, mainly. Then the waffles themselves, in many incarnations: whole-grain sourdough, rocky road, mustard, zucchini-cheddar, rhubarb, chocolate-amaretti. There is a tiramisu waffle, a lemon meringue waffle and a white chocolate-chip variant--all lavish, as expected. And Greenspan doesn't neglect the childish sweet-tooth: one chapter is entitled ``Just for Kids.'' So while it still seems unlikely, at the end of all, that anyone will actually grill up waffles for every meal, that possibility, as Greenspan presents it, is a pungent fantasy. (Aug.)